A platinum-group-containing layer may be applied to the surfaces of a substrate to improve the corrosion resistance and oxidation resistance of the substrate. The platinum-group precious metals do not react to any substantial degree with oxygen, exhaust gas, or most other common oxidants and corrodants. The result is that the substrate with the platinum-group-containing layer thereon is at least partially inert in such environments. Platinum-group metals are expensive, but the improvement in properties produced by even a thin platinum-group-containing layer often justifies the cost.
One approach to applying a platinum-group-containing layer is electrodeposition. The substrate to be protected is made the cathode of an electrochemical cell in which the electrolyte is a platinum-group-containing salt. The application of an electrical current results in the deposition of the platinum-group metal onto the substrate. Electrodeposition is slow and can be difficult to apply in practice, such as in conditions where the substrate is irregularly shaped or the platinum-group layer is to be deposited only in selected areas of the surface of the substrate.
An alternative approach that has been considered is to apply the platinum-group metal from a platinum-group-containing paint. The proposed approaches are not environmentally acceptable, because they release volatile organic components during one or more of the processing steps.
There is a need for an improved approach to the deposition of a platinum-group-containing layer on a substrate. Such an approach must be compatible with other processing steps and be environmentally acceptable. The present invention fulfills this need, and further provides related advantages.